Theories abound as to the origin of bad banana power, including:

The Spanish observed a statistically significant number of their ships that were lost between the Americas, Caribbean and Europe in the 1700s were carrying bunches of the bad luck fruit

Fermenting bananas below deck were believed to release poisonous methane gas

And the poisonous spiders that hopped aboard in the bunches might take up residence endangering future crew – making the boat bad luck